In casting production, a cavity is usually formed in a casting by means of a core, in order to reduce its weight. For example, a camshaft, a crank shaft, and the like, which are the constituent parts of an automobile engine, have conventionally been solid but have recently adopted a hollow structure. The cavity of a casting is formed by a core, thereby attaining a considerable weight reduction. Since a camshaft, a crank shaft, or the like has a long overall length, a long core must be used. When a long core is set on a mold, the core may deflect or be broken due to its length and weight. When melt is poured, a core undergoes buoyancy of the melt and floats in the mold, with the result that wall thickness of a casting becomes non-uniform. Alternatively, the core is broken, thereby making it impossible to obtain a product.
Chaplets having various shapes are used as a counter-measure to cope with the above-described problems.
Non-Patent Document 1 describes that the functions of a chaplet are as follows. (1) A chaplet supports the weight of a core and maintains its size. (2) A core may float under the pressure of melt during casting; a chaplet is resistant against the core floating. (3) A chaplet withstands until a casting solidifies somewhat and hence prevents displacement of a core. (4) A chaplet is desirably fusion-bonded with the melt and is incorporated into the casting. These functions of a chaplet are matters of common technical knowledge for a person skilled in the art.
Patent Document 1 discloses production of a long casting, such as a camshaft or a crank shaft by using a core and a chaplet. An annular chaplet body extends around the outer periphery of a core except for a gap that also extends around the outer periphery of a core. Legs of the chaplet radially extend from the chaplet body. The chaplet is engaged on and is brought into contact with the wall of a mold. The chaplet is incorporated into a workpiece upon solidification of melt.
In addition, Patent Document 2 discloses a mounting structure of a chaplet. According to this structure, a chaplet body consists of one wire and is inserted in a groove of a core, and a plurality of contact parts extend radially from the chaplet body, and are engaged on and brought into contact with the wall of a mold. An aperture is formed between a pair of the contact parts. The groove of a core consists of an insertion portion of a chaplet and a fixing part for axially displacing and fixing the chaplet.
Non-Patent Document 1: Lecture of Metal Engineering 5, Working Edition, edited by Yunoshin Imai, Asakura Bookstore, published on Feb. 15, 1972, pages 124-125
Patent Document 1: Japanese Published Patent Application (kokai) No. 2004-66429
Patent Document 2: Japanese Published Patent Application (kokai) No. 2006-102750